جستجوی مقالات مرتبط با کلیدواژه « طراحی آزمایش » در نشریات گروه « مکانیک »

Due to the importance of the weld quality in pressurized equipment, this research investigates the application of Nd:YAG pulse laser in welding of thin-walled AISI316L steel pipes. The input parameters include current intensity, pulse width, frequency, rotational speed, and compressive force applied to the seam of the two tubes being welded. Depth of weld penetration and the weld depth-to-width ratio (aspect ratio) were selected as two output characteristics. The relationship between input and output parameters was obtained by fitting regration functions on the data of central composite design (CCD) of experiments. According to the analysis of variance, the influence of the ratio of compressive force applied to the weld seam to the aspect ratio is 2.5%, and total influence of pulse width and the current on each of the two outputs is 84%. Completion of the depth of penetration and increasing of the weld aspect ratio are two main findings of the optimization process. In the end, to improve the joint quality, based on the optimal level of the parameters, samples were laser-welded in a chamber filled with argon. With this regard, aspect ratio, tensile strength, and failure strain at the samples manufactured by optimum parameters in argon chamber, were improved by 14%, 7%, and 37% compared to samples in normal condition (protection of the molten pool with an argon nozzle), respectively.

The significance of sheet metal drilling within industrial applications is widely recognized, particularly for its critical role in creating durable connections in sheet components. This process, especially when implemented through friction drilling, not only minimizes material waste by generating connecting flanges bush shape but also enhances the robustness of the connections. In this study, we used the ABAQUS finite element software (FEM) to simulate and design the friction drilling process on sheets of three different thicknesses, employing three rotational speeds and three feed rates. The analysis was conducted using Design Expert statistical software, which integrated response surface methodology (RSM) and data analysis to thoroughly investigate the process forces. Aluminum AA 7075 was selected for the study due to its extensive use in the automotive, manufacturing, military, and aerospace organizations, highlighting its industrial relevance. The findings suggest that optimizing the machining force leads to more favorable conditions within the process. The optimal parameters were determined to include the highest rotational speed, the lowest feed rate, and the smallest sheet thickness. These conditions promote higher temperatures that facilitate better material flow. An increase in thickness was also found to correlate with higher temperatures. Additionally, the study addressed the significant industrial challenge of residual stresses and their effects on component defects, a topic not previously explored through finite element simulations in this context. This research contributes new insights into the implications of residual stresses in various directions for friction drilling processes.

In this article, the mechanical properties of biocomposites reinforced with kenaf fibers/nanographene in the field of polypropylene with the addition of PP-G-MA compatibilizer have been investigated. Response surface method (RSM) with Box-Behnken Design (BBD) has been used to investigate and present a mathematical model for the behavior of biocomposite according to the parameters of weight percentage of Kenaf fibers, nanographene, and PP-G-MA. The behavior of the samples was analyzed under tensile, bending, and impact tests, and the results were confirmed using FE-SEM images. The failure surface of the samples showed that the main mechanism in improving the behavior of the introduced biocomposite is the failure of the fibers and their separation along with the stretching of the fibers from the base material. The multi-objective optimization process was performed using two methods metaheuristic and utility function. Optimization was carried out to increase flexural strength, impact resistance, and tensile strength while simultaneously reducing the weight of the specimens. The weight percentages of fibers, nanoparticles, and compatibilizer were defined as the variables of the problem. The results showed that the values of the biocomposite sample in the optimal state for three mechanical properties including tensile, impact, and bending strength are 28.5 MPa, 92.29 J/m, and 50 MPa respectively. At the end of the optimal mode, it showed that the weight of the biocomposite can be reduced by 32%.

This paper investigates the deflection of chromium nanobeams using the design of experiments method. Using the full factorial method, a number of 100 experiments were designed in which the length and the force on the nanobeam were considered input variables at 25 and 4 levels, respectively and the deflection of the nanobeam was considered output. First, all 4 force levels (8, 9.5, 11, and 12.5 nN) were used for the analysis, and closed-form equations were obtained to estimate the deflection of the nanobeam. The results showed that the effect of the length is more than the force, by increasing the length so that the deflection changes with third degree. The third-order regression model predicts the deflection with high accuracy, and its error value is lower than the first and second-order regression models. Afterward, two levels of force (8 and 11 nN) were used for analysis, and new equations were obtained to estimate the deflection of the nanobeam. The new equations were used for interpolation and extrapolation of the nanobeam's deflection in forces of 9.5 and 12.5 nN, respectively. The results demonstrated that the regression model using two force levels accurately predicts the deflections of nanobeams as well. The results of this research demonstrated that it is possible to estimate the nanobeam's deflection without the need to perform more experiments and spend cost, perform complex calculations, and solve differential equations; the nanobeam's deflection can be accurately estimated with algebraic formulas.

The combustion flow field in domestic gas stove burners plays a fundamental role in the structure and shape of the flame, the distribution of the temperature gradient, and, consequently, the thermal efficiency and emission of pollutants. Obtaining a valid numerical model makes it easier to understand this complex flow and its influencing factors. To provide a valid numerical simulation, the thermal efficiency of the burner was experimentally tested in the pressure range of 12 to 24 mbar. The validity of the numerical results was then examined by comparing them with the experimental results. Additionally, the response surface methodology was utilized to investigate the simultaneous and mutual effects of various factors such as gas source pressure, initial temperature of the mixture, and load height on thermal efficiency, burner thermal power, the ratio of radiant heat flux to total flux, and the amount of CO emission. The algorithm proposed 20 cases that were numerically investigated, and the obtained contours were extracted based on the fitted regression models for the output parameters. The results show that although increasing the pressure increases the thermal power of the burner, it decreases its thermal efficiency. As the pressure of natural gas decreases, the flame temperature increases and the temperature peaks approach each other. In fact, the concentration of the flame increases with the decrease in pressure, and as a result, the thermal efficiency increases. Additionally, the results show that CO gas emission decreases with increasing pressure.
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In this research, the effect of various operating conditions on the performance of an Unmanned Aerial Vehicle (UAV) with a PEMFC propulsion system is surveyed using a statistical approach, namely the Design of Experiment technique (DOE). This process starts by designing a thermodynamic cycle for UAV based on the literature review. Then, a zero-dimensional model is established to simulate the PEMFC’s performance. After validating the developed model for PEMFC, mass and energy balance equations are employed for all components of the thermodynamic cycle to calculate the efficiency of PEMFC and the system simultaneously. Afterward, the Response Surface Method (RSM) is used to design appropriate tests to study the influence of independent variables, i.e., altitude, operating pressure, and cathode stoichiometry, on the efficiency of PEMFC and system. Results indicate that increasing operating pressure improves the efficiency parameter for both the PEMFC and the system 3.5% and 14.5% respectively. Although increasing cathode stoichiometry augments the PEMFC efficiency, it plummets the system efficiency up to 30.6%. In addition, the influence of operating altitude on the PEMFC efficiency is negligible, while it causes a substantial decline in the system efficiency (more than 30%). As proved, at any desired operating altitude, maximum efficiency for the system obtains when the operating pressure and cathode stoichiometry are set at their maximum and minimum bound, respectively.

One of the main methods for strengthening and increasing the hardness of the materials is the use of the severe plastic deformation (SPD) processes. Equal channel angular pressing (ECAP) method is one of the SPD methods. Two challenging issues including (1) the very high required punching force, and (2) the deflection of the punch restrict the application of the method in industry. In this paper, a new design of ECAP process is proposed, which in addition to reducing the punching force, eliminates the deflection problem. The main purpose of this paper is to investigate the effect of the process parameters including process temperature (100- 200-300) ° C, lubrication (dry and graphite) and the number of ECAP passes (1-2-3) on the hardness of 7075 aluminum material and determining their optimal levels. The Taguchi design is used for design of experiment and the S/N ratio is used to find the optimal levels of the parameters and to maximize the hardness of the material. Based on the analysis of the variance, the process temperature and the number of ECAP passes have the greatest effect on the hardness of the post ECAP samples. However, the lubrication condition has not a significant effect on the hardness of the post ECAP samples in all temperatures.

Cyclones are devices used to separate two or more phases from each other. Cyclones are centrifugal particle collection systems that use the effect of a tornado to separate solid particles from the gas stream. The purpose of this article is to investigate the effect of 5 inlet parameters including inlet height, inlet width, outlet diameter, total cyclone height and body cyclone height on both pressure outlet and cut-off diameter. These parameters have not yet been investigated by Sobel analysis. In this article, the effect of 5 cyclone inlet parameters including inlet height, inlet width, outlet diameter, total cyclone height and cyclone body height on two outlet parameters including pressure drop and shear diameter was investigated through their regression equation and Sobel statistical sensitivity analysis. So far, the effect of these 5 parameters on these outputs has not been investigated through Sobel statistical sensitivity analysis. The results show that inlet width with 40%, inlet height with 36% and outlet diameter with 24% had the greatest effect on pressure drop, respectively, and the height of the cyclone and the square height of the body had no effect on pressure. On the other hand, the inlet height with 40%, the inlet height with 38%, the height of the cyclone with 12% and the body height of the cyclone with 10% have the greatest effect on the shear diameter, respectively, and the cyclone outlet diameter has no effect on the cut-off diameter.

Providing fresh water has been one of the most important concerns of mankind and various methods have been used to solve this concern. In this regard, one of the simplest devices is the stepped solar still. In this research, the effect of using fabric as an absorbent material and its related parameters on the amount of freshwater production has been investigated experimentally. In this regard, stepped solar still has been built and the parameters related to the fabric and their interactions have been tested. These parameters were: type, color, number of layers, and the angle of the fabric relative to the surface of the steps, as well as the height of the water weir in each step. The experiments were designed using the Taguchi method. Among the examined parameters, the color and the material of the fabric have been identified as the most effective factors in increasing the volume of produced fresh water. The results showed that the maximum water production during the day was 2790 ml/m2 using black cotton fabric in three layers with an angle of 90 degrees relative to the steps' surface and a water weir height of 1 cm.

Population growth and freshwater scarcity have led people to think about renewable energy sources. In this research, a stepped solar still has been used to produce drinking water. In order to improve the device's performance, absorbent fabrics were utilised to increase the heat transfer area between the saline water and the environment, resulting in increased evaporation and fresh water production. Water inlet flow rate, fabric material, fabric thickness or number of layers, fabric colour, and fabric placement angle are all variables that have been used at the same time. Three different fabrics in three different layers were used in the experiments, with flow rates of 50, 100, and 150 ml/min and angles of 30, 60, and 90 degrees. There were also three colours for fabrics: white, brown, and black. The response level approach was used for the design of the experiments in this study, and 27 experiments were examined. The findings revealed that the black color, material # 1 with the highest water absorption, more layers, larger angles of fabrics, and lowering the flow rate all had an effect on increasing the amount of fresh water produced.

An investigation has been conducted to determine the optimum blade planform required to minimize the rotor power, maximize the lift-to-drag ratio, and maximize roll attitude quickness of the helicopter using numerical optimization techniques. The optimization process is based on response surface method, I-optimal design expriment, and helicopter inverse simulation program (HISP), developing mathematical model of performance, and Turning a multi-objective optimization problem into a one-objective problem using Desirability approach that the optimal numerical solution will eventually be calculated. The effects of helicopter weight and blade planform parameters (i.e., root chord, taper ratio, the taper starting point on the blade, and blade twist) on the performance and handling quality of the helicopter are therefore investigated. Responses of helicopter were obtained through a HISP developed for rotors with quasi-steady aerodynamic formulations. The resulting system provides a systematic evaluation to examine the rotor blade design variables and their interactions, thus reducing the time and cost of designing rotor blades. The results also confirm that the optimum tapered blade lowers the power required by about 7% and enhances the lift-to-drag ratio and roll attitude quickness up to 10% and 36% with a satisfactory improvement relative to the helicopter with rectangular planform a NACA 0012 cross-section in slalom maneuver, which is a good improvement for rotor blade design.

Magnetic abrasive finishing process (MAF) is one of the latest advanced machining processes. After eight decades have passed since the registration of the magnetic abrasive polishing process, the applicability of this method has been proven in finishing all kinds of surfaces, including flat, cylindrical and free surfaces. In this research, the influence of MAF process movement parameters on the concave surface of cold-worked steel has been investigated experimentally using the response surface method. These parameters include rotational speed, linear speed, gap between abrasive brush and workpiece, magnetic flux density and curvature angle. For this purpose, a spherical head magnet is used and the powder used is prepared by mechanical alloying method. Cold-worked steel is used in the manufacture of roll forming molds, which is used in air engines to shape compressor and turbine blades, and also to investigate the feasibility of the MAF process on the workpiece surface with high hardness and yield stress, such as Cold work steel is selected. According to the results, the optimal value of the magnetic flux density is 0.55 tesla, and with the increase of the distance between the abrasive brush and the workpiece, the surface roughness changes initially increase and decrease after passing the optimal value.

Today, additive manufacturing methods have found wide applications in various industries due to their many advantages, including not needing tools and molds, as well as short production time. Among these methods, the FDM process is widely used due to its cheapness and ease of production. As a result, it is very important to discover the relationship between the mechanical properties of the product produced in this way and the parameters used in the process. In this research, the effects of layer lamination angle, infill extrusion width and layer thickness on the normal force and tensile strength of PLA printed samples are examined. In order to investigate the effects of the parameters, the design of experiment, using surface response and Box-Benken method was used with the help of Minitab software. The results of the tests show that the maximum tensile strength and normal tensile force of the printed samples were equal to 38.36 MPa and 1.50 kN, respectively, which is at zero-degree lamination angle, infill extrusion width of 150% and the thickness of the layer 0.3 mm.

Due to the importance of the joints in the pressurized instruments and the abilities of the laser welding in this study, the welding of AISI316L tubes have been studied and analyzed. In this regard a fixture has been drawn in order to positioning of the tubes and fixed on the welding desk. The welding input parameters includes the laser welding adjusting variables, includes (welding current, welding pulse width, and welding frequency). Moreover, the effect of the two other variables (rotating speed and the force applied to the welding seam) has also been studied. The welding output characteristics comprises the welding width, depth of penetration and welding strength. The experimental data has been collected using L27 Taguchi design. The relation between the process input variables and output characteristics has been established using different regression models. Based on the analysis of variance (ANOVA) results, pulse width and welding current with 70% contribution have an influential effect on all the three response characteristics. Moreover, the seam force has only the influential effect on the depth of penetration and strength. Next, in optimization step based on the importance of the process characteristics (strength, depth of penetration, welding width), the optimized levels have been determined. At the end, the optimized condition has been conducted using laser welding, in comparison of which the samples in the design matrix, the welding depth has a close relation with the thickness of the wall, the welding boundaries smother and the strength has a close value to the base metal.

In the present study, the thermal performance of the air-side compact heat exchanger of an automotive condenser in the three-dimensional model has been numerically simulated based on the design of experiment (DOE). For this purpose, the effective geometrical parameters such as fin pitch, louvre pitch, louvre angle, fin height and fin width and their effects on condenser thermal performance are studied and investigated. Finally, for parameters effective on the compact heat exchanger operation, such as air-side heat transfer coefficient, static pressure drop and other thermal parameters, relationships are extracted based on the design of experiment which decrease the computational cost with the least error. The results show quantitatively that by increasing the fin length, louver angle, louver pitch and decreasing the fin pitch, the heat transfer rate increases by about 42%. Also, the results show that the heat dissipation, heat transfer coefficient and pressure drop, have improved by 8.1%, 5% and 10.5% respectively compared to recent numerical results. Eventually parametric studies including the effect of ambient temperature, condenser wall temperature and vehicle speed on thermal performance and pressure drop are presented.

In the process of polishing with magnetic abrasive particles, several parameters affect the smoothness of the final surface of the part. These parameters include properties related to machining conditions, workpiece properties, or abrasive powder properties. The present paper deals with the effect of the kinetic parameters of the MAF process on the convex and concave surface of aluminum alloy experimentally. These parameters include rotational velocity, linear velocity, abrasive brush distance to the workpiece (gap), magnetic flux density, and angle of curvature. For this purpose, a spherical head magnet was used and the powder used was prepared by mechanical alloying method. Also, the two-way zero-degree raster movement strategy is used for the tool movement path. The experiment was designed using miniatub software. According to the results of analysis of variance, it was found that all the main factors or their interaction are effective. Also, the roughness changes on the convex surface are more than the concave surface. On the convex surface, the roughness changes with increasing curvature angle. On the convex surface of the workpiece, with increasing magnetic flux density, there is an increase in surface roughness changes, while on the concave surface, passing the magnetic flux density of 0.53 Tesla, the progression of roughness changes occurs. The effect of velocity on the convex and concave surfaces of the workpiece is the same, and with increasing rotational speed from 125 to 2000 (rpm), the roughness changes of the concave surface of the workpiece increase by 57%.

The propulsive force in an unmanned aerial vehicle is usually produced by propellers and the UAVs require maximum propulsive force and minimum drag force to perform various operations. The aircraft's performance is influenced by the spinner shape; therefore, accurate analysis of its aerodynamic shape can improve the performance. In this research, the aerodynamic design of the spinner and the geometric parameters effective on the UAV performance are mentioned. The ultimate goal is to use an optimized spinner for dual-propeller UAVs. Initially, the effect of spinner geometry on the aerodynamic features of the pusher propeller is investigated. Then, a numerical simulation based on computational fluid dynamics is done and the outcomes for both the presence and the absence of spinner are compared. In the numerical simulations, the flow field is considered as three-dimensional, unsteady and turbulent, and these results are compared with the published data for verification of the numerical procedure. The research's motivation is to improve five design variables in the design of pusher propeller spinner namely,  (the radius of reference plane),  (the reference length),  (the gap between the spinner and cowling),  (the reference slope angle), and  (the slope angle of spinner cap) and to provide solutions to select the appropriate spinner by an efficient method such as the Taguchi method. This process is followed in such a way as to achieve the desired propeller performance as an objective function. Eventually, the optimum spinner which achieves improved performance, increased propeller propulsion efficiency and declined fuselage drag force is obtained.

The calibration of modern internal combustion engines is complex and requires a lot of time and cost on the test bench. A large number of calibration parameters and a tradeoff between fuel consumption and emissions make calibration a complex multi-objective optimization problem. The purpose of this article is the development of calibration and model-based optimization techniques for internal combustion engines to reduce calibration time and cost and improve optimization accuracy. This paper focuses on empirical modeling of engines and optimization concerning emissions standards and fuel consumption. To identify the combustion models, a modeling toolbox is developed with an intelligent identification method. To optimize the data collection, the design of experiment methods is reviewed and appropriate methods are selected to collect information with the minimum data from all over the design space. Finally, a study is performed on the EF7 engine in the test room of IPCO and it is shown that the number of experimental data is reduced from 5500 data to 1500 data with the help of the design of experiment by Sobol method and modeling by a deep neural network. so, the virtual engine can replace the real engine in the calibration process.

In this research, the effect of anode stoichiometry, cathode stoichiometry and temperature of inlet gases on water management and performance of a PEM fuel cell is studied by means of DOE (Design of Experiments) and direct visualization. In order to visualize the liquid water accumulation in cathode flow channels, a transparent PEM fuel cell is designed and manufactured in fuel cell research laboratory of Amirkabir University of Technology. Design of experiments is based on response surface method and central composite design. Cell’s performance is recorded over the test time and a video is simultaneously captured from its transparent cathode flow channels. Then, a digital image processing technique is used to detect and quantify channel areas that are occupied by liquid water. Area of regions containing liquid water is divided by total area of flow channels to calculate a parameter called water coverage ratio (WCR) which is then used to study flooding phenomenon. Results show that increase in cathode stoichiometry, anode stoichiometry and gas inlet temperature leads to a decrease in WCR. Also, WCR lies between 1.8 and 4.3 when an optimized produced power is reached. It is also proved that anode and cathode stoichiometry has to be minimized to reach the maximum produced power at a high inlet gas temperature.

Bio-fouling as a worldwide marine industries concern is the accumulation of micro and macro-organisms on the submersed surfaces in the sea water. It has destructive effects on the sunk parts of the ships, fish cages and all other marine submersed structures. To reduce bio-fouling on the nylon fibers a dual mix of 2-Hydroxy ethyl methacrylate(HEMA) and methyl acrylate(MA) was grafted on the fiber surface using a pre-irradiation technique in different conditions. Subsequently, degree of grafting and homo and or co-polymer % of the aforementioned monomers at different operative parameters including reaction temperatures (60-90℃), and times (1-4h), pre-irradiation time (10-40min) and also initiator concentration (3-9wt%) were measured and the results were compared and discussed with those calculated values by a traditional design of experiment software (Design expert®). The optimum grafting conditions and the interaction between above mentioned parameters were evaluated by the software using four variables and two surface responses with central point design method. It found that increasing pre-irradiation time and also initiator concentration improved the grafting % of the monomers on the fiber surface. The reason referred to increasing the active sites on the fiber surface after pre-irradiation. With the aid of variance analysis and considering p-values variable with 0.05 confidence interval, it revealed that the important parameters lied down in the order of reaction temperature, reaction time, pre-irradiation time and initiator concentration. Also, the results were confirmed statistically by the characteristic coefficient, adjustment coefficient and fit precision of 96%,93% and 30.302, respectively. The real values for degree of grafting and also homo and co-polymer percent were 47.9% and 41.15% respectively. They were in conformity with predicted values by mathematical model with the values of 38.59 and 43.42%. Also, two equations were proposed by the software for calculation of the aforementioned parameters with studied operative parameters.